The present invention relates to a flow machine with a compressor and at least one turbine, with a booster stage with one or more booster elements arranged in the intake duct of the compressor, and also to a process for the optimized operation of such a flow machine.
The present flow machine is suitable for the embodiment of a gas turbine, gas turbine plant, or combination plant, principally for energy production under the condition of the use of different fuels, under changing ambient conditions, and also special supply network requirements.
A gas turbine is known from U.S. Pat. No. 3,979,903 in which a booster fan is arranged in the intake duct of the compressor. This booster fan is driven by a separate turbine at about constant power and makes possible, among other things, an increased power of the gas turbine plant.
It is also known to insert one or more such booster fans in the intake duct of the compressor of gas turbine plants. These so-called air intake boosters increase the mass flow of air, leading to a power increase of the gas turbine plant They are therefore used at peak load times or when it is necessary to provide additional reserve power, etc. Furthermore, effects on the power of the gas turbine plant due to seasonal, locational and climatic influences can be compensated for by the operation of this booster fan.
A further possibility for power increase of a gas turbine plant consists in the arrangement of one or more booster fans in the exhaust gas duct of the turbine. These so-called exhaust gas boosters lead to a reduction of the pressure in the exhaust gas duct and thus to an increase in the expansion drop of the hot gases emerging from the turbine. The increase of the expansion drop furthermore results in a power increase of the gas turbine plant. The booster fans in the exhaust gas duct can, like the air intake boosters, be switched on in peak load times and also when it is necessary to provide additional reserve power. They can likewise be used for the compensation of seasonal, locational and climatic influences on the power of the gas turbine plant.
The present invention provides a flow machine and also an operating method for the flow machine, which make possible a smooth manner of operation of the plant, which is improved over the state of the art, and also is optimized as regards climatic, locational and design influences, changing fuels, and different supply network requirements.
The present flow machine, which is equipped in known manner with a compressor for the compression of the combustion air intake, and also at least one turbine, has a first booster stage which is arranged in the intake duct of the compressor. The flow machine furthermore has a second booster stage arranged in an exhaust gas duct which adjoins the at least one turbine directly or via intermediate elements.
The first booster stage and/or the second booster stage can also be arranged in already existing, or additionally installed, bypass ducts to the respective intake duct or exhaust gas duct.
The use of such booster stages in conventional systems was only either in the intake duct or in the exhaust gas duct in order to adjust the pressure conditions there, corresponding to the specific requirements of the respective flow machine. The inventors of the present flow machine have discovered, however, that by means of the combined use of both booster stages in a flow machine, an optimized mode of operation of this flow machine is made possible over a very wide range of operation.
The first booster stage and the second booster stage serve to optimize the whole intake region as far as the inlet of the intake air into the compressor, and the whole exhaust gas region up to the exit of the exhaust gases from the turbine, both from a structural perspective and also with regards to flow technology.
The first booster stage and/or the second booster stage can be respectively constructed as a single (large) booster element or plural (small) booster elements. The individual booster elements of a respective booster stage can be arranged in a series or parallel arrangement with respect to the intake air or the exhaust gas. The arrangement of the booster elements is furthermore independent of items built into the intake duct (e.g., air filter) and exhaust gas duct (e.g., noise control elements). The booster elements of a booster stage can be arranged before, after, or both before and after an installed item.
The fans of the booster elements are preferably driven by speed-controlled drives. The power requirements of the first and second booster stages can be minimized by means of a suitable control. In order to be able to operate the booster elements for special purposes even when the supply network power fails, a design of the drives of the booster elements as low voltage drives is advantageous.
For an economical operation of the first and second booster stages, it is furthermore appropriate to equip the fans of the booster elements with adjustable fan blades.
Since the exhaust gases of the turbine have a very high temperature, it is furthermore appropriate to use the exhaust gas heat in a heat recovery system before discharge of the exhaust gases into the atmosphere. Waste heat boilers for producing hot water or steam particularly are useful for this purpose.
With this mode of construction, a flow machine is implemented which has both so-called air intake boosters and also so-called exhaust gas boosters. Just the possibility of use of the two booster stages either singly, i.e. in a different sequence, or in combination, i.e., simultaneously with possibly different power, makes it possible to optimally adjust the mode of operation of the flow machine respectively to varying operating conditions. Varying operating conditions arise, for example, in dependence on the ambient conditions, the load conditions of the whole plant, the fuel used, and also on the supply network requirements.
Since both the air intake booster and also the exhaust gas booster contribute to the increase of power and also to an increase of efficiency, both booster stages are to be in operation during normal operation. This is particularly so when, due to a high current or power requirement in the supply network, high current remunerations can be attained. The same is true when reserve power is required or is to be offered at short notice. This holds also, however, for power equalization with the use of a qualitatively worse fuel.
If the flow machine is put to use for the purpose of frequency regulation, i.e., for regulation of the national supply network frequency, this means an oscillating mode of operation with a very high dynamic load, particularly on the thermally loaded components of the hot gas path. This power delivery, oscillating in a small power range, is now undertaken by the first and/or second booster stage(s).
In times when the power supply load is abating, i.e., in times of decreasing current remunerations, the less efficient exhaust gas booster can first be taken out of operation, followed by the air intake booster. In a further step, the forward guide blade row on the compressor can be closed, and after these potentials have been exhausted, the entry temperature into the turbine can still be lowered.
An individual operation of a respective booster stage thus preferably presents itself in the region of partial load operation, or to fulfill special requirements. The buoyancy conditions of the exhaust gas flowing out of the exhaust gas duct are also improved by the use of the exhaust gas booster. An exhaust gas booster can ensure buoyancy conditions analogous to a reduction of the height of the exhaust gas duct, in comparison with a clearly; higher exhaust gas duct. The operation of the exhaust gas booster can however also contribute to the improvement of the emission conditions in unfavorable or extreme weather conditions.
Before or during the startup of a flow machine, it is important to ensure that no combustible substances remain in the system by a flushing process of the whole system. This flushing process is usually implemented by rotating the shaft line. Flow conditions in which combustible substances are blown out of the system are to be attained by means of the compressor. Furthermore, for starting a flow machine, the shaft line has to be accelerated up to a predetermined rpm before the beginning of firing. A further acceleration is required in order to attain self-supporting operating conditions. The acceleration and the rotation of the shaft line to or at a relatively high rpm is at present usually implemented by means of a starting converter and an operation of the generator as a motor.
An efficient flushing of the gas turbine plant and of the exhaust gas system can now be attained by the operation of the first and/or second booster stage(s), particularly in connection with the use of waste heat boilers for steam production downstream of the at least one turbine during the starting of the gas turbine plant.
For example, for shortening the inspection times of flow machines, it can be appropriate to possibly additionally cool these, already during, but particularly after, stopping. This additional cooling, termed xe2x80x9cforced coolingxe2x80x9d, is furthermore usually implemented in that the shaft is turned by means of the startup converter and the generator, and cold air is flowed through the flow machine by means of the compressor. The same task can now be implemented by means of the first and/or second booster stage.
The operation of the booster stages can also contribute during power increases or during normal operation to having the flow machine run more smoothly, or to implement greater power gradients. Thus it is possible, with incorporation of the first and second booster stage during startup or when there are power increases, to implement a greater power gradient, or to run the plant more smoothly at the same power gradient and reduce firing power. Even in stationary operation it is possible, in dependence on the specific conditions, to reduce the firing power of the flow machine when implementing a comparable plant power, so as to reduce the upper process temperatures in order thus to reduce, in particular, the thermal loading of the components.
The design possibilities and modes of operation which have been described by way of example show that by means of the total of the measures and their combination, a further range of possibilities for the design and the optimization of the operation of a gas turbine or combination plant is available under the operating conditions present at any given time.
The equipment of gas turbines or combination plants with air intake boosters and exhaust gas boosters is of course not limited to new plants. These boosters can also be retrofitted to existing plants for the compensation of, for example, aging effects. They can also be used, however, for raising power and efficiency, for adjustment of the power to the requirement structure, and the like.